SOCRATES

As a service to the satellite operator community, the Center for Space Standards & Innovation
(CSSI) now offers SOCRATES—Satellite Orbital Conjunction Reports
Assessing Threatening Encounters in Space. This service will provide regular
information on pending conjunctions on orbit over the coming week. Because of
the potentially catastrophic consequences of such conjunctions going unnoticed,
it is hoped that this service will help satellite operators avoid undesired
close approaches through advanced mission planning.

Methodology

Twice each day, CSSI runs a list of all satellite payloads on orbit against a
list of all objects on orbit using the catalog of all unclassified NORAD
two-line element sets (TLEs) releasable to the public to look for satellite
conjunctions over the next seven days. The reason for limiting the search to
conjunctions with payloads is to give satellite operators an opportunity to
plan—or obtain planning services—to move their satellites out of
harm's way (if their satellite is maneuverable), or to take other appropriate
measures. Since there currently is no way of knowing which payloads are still
active, all payloads are considered.

The runs are made using, STK/CAT—STK's
Conjunction Analysis Tools—and the SGP4
propagator in STK. STK/CAT is set to look for all conjunctions which are
within 5 km at time of closest approach (TCA) and reports both minimum distance
and maximum probability for the conjunction. Because the minimum distance method
ignores position covariance information and can lead to an exaggerated
assessment of the true risk, CSSI believes the maximum probability method
provides a more reasonable (although still conservative) assessment of the true
risk. For more details on the maximum probability method, see Dr. Sal Alfano's
paper titled "Relating Position Uncertainty to Maximum
Conjunction Probability" (2,493,912 bytes).

[Now available] Ability to download complete, ready-to-run
STK/CAT scenario for each conjunction to facilitate additional analysis.
Update: CelesTrak received authorization from Air Force Space
Command to provide TLEs in support of SOCRATES on 2005 March 24 (see the
System Notice for details).
The original capability to build full STK/CAT scenarios has now been
restored.

AGI Viewer files for the Top 10 conjunctions (a sample AGI Viewer file from the 6th
US-Russian Space Surveillance Workshop paper is now available (932,839 bytes)
and the free AGI Viewer software can be obtained on CelesTrak here).

[New: 2007 Sep 19]Ability to bookmark
searches for future use. A link to bookmark each search will appear at the top
of the Search Results page. This feature should make it easy for satellite operators
to repeat searches of interest or to build a custom page with those links.